DESCRIPTION: The investigators propose to test the feasibility of developing efficient, actively switched radiofrequency transmit and receive coils based on transverse electromagnetic (waveguide) principles for use in magnetic resonance imaging at 3 Tesla and above, as further described by their abstract: "The investigators plan to prove the feasibility of an efficient homogeneous transmit coil for human NMR studies at high field strengths (3T-4T). Such a coil will be unique in high field human applications. Significantly this homogenous transmit coil for human heads and bodies will facilitate the extension of the present 1.5T clinical MR transmit and receive imaging methods to the growing number (now 35), of 3T and 4T systems now operating or being delivered world wide. These favored transmit and receive imaging methods make use of a large transmit (body) coil, paired with a local surface coil or a phased array coil receiver. The large transmit coil is used to generate a homogeneous B1 field. The local surface coil or phased array then receives an NMR signal response with a high signal-to-noise (SNR) ratio from a localized region of interest (ROI). These independent transmit and receive coils must be actively decoupled from each other during transmit-receive operation. This decoupling requires both transmit and receive channel switching with a TR switch, and alternate transmit and receive coil detuning circuit. The overall goal of this project is therefore to develop, build, and test an actively switched and detuned RF transmit coil for efficient operation at 3T to 4T. This RF coil system consists of 5 functional components; the development of each component will be a Specific Aim. The demonstration of feasibility will be to prove that each of the coil system components meet their respective design specifications, followed by the successful testing of the assembled sum of these components in RF transmit coil system. In Phase I, this high field transmit coil system will be developed for human head imaging. In Phase II, this coil will be scaled for human body imaging." PROPOSED COMMERCIAL APPLICATION: 3T and 4T Head and Body Coils for the MRI industry.